Three very long, straight wires lie at the corners of a square of side d, as shown in the figure. The currents in the three wires have the same magnitude i, but the two diagonally opposite currents are directed into the screen while the other one is directed out of the screen. d i& Derive an expression for the magnitude B of the magnetic field at the fourth corner of the square. B = Enter your expression in terms of given quantities, the permeability of free space o, and exact rational and irrational coefficients. Determine the direction of the magnetic field at the fourth corner of the square, measured counterclockwise from the 0 = positive x-axis. d y X